This invention relates to an electric rotary machine equipped with a stator coil including sequentially connected conductor segments (which is also referred to as xe2x80x9cserial-joint segmental stator coilxe2x80x9d, in the following description), which is preferably applicable to an automotive vehicle.
According to the idle stop system recently employed for automotive engines, the engine is frequently required to stop and restart. Large current is required for restarting the engine. Thus, for the idle stop system, using an excellent starter motor capable of surely supplying large current is essentially important.
In this respect, a serial-joint segmental stator coil is simple in the wiring arrangement at its coil end, large in the slot space factor, compact in the size, and light in the weight. Accordingly, the serial-joint segmental stator coil has excellent heat radiation properties and is preferably employable in an altering-current motor supplying large current to frequently restart the engine.
Enlarging the cross-sectional area of a conductor segment in the stator coil is effective in increasing the current flowing in an electric rotary machine. However, difficulty in bending the conductor segment will limit the increase in the cross-sectional area of a conductor segment.
Meanwhile, to increase the output of an automotive electric rotary machine and also reduce the wiring loss in this machine, not only increasing the current but also increasing the voltage will be necessary. In other words, the turn number of the coil will be increased inevitably.
In view of the foregoing problems of the prior arts, an object of the present invention is to provide a stator coil preferably used for a starter motor or a comparable electric rotary machine which is operable under high current/voltage power sources.
To this end, the present invention provides a stator coil including sequentially connected conductor segments for an electric rotary machine which is capable of simplifying the connection pattern of conductor segments.
Furthermore, the present invention provides a stator coil having a parallel circuit arrangement capable of suppressing variation in the electromotive force occurring between parallel circuits.
To accomplish the above and other related objects, the present invention provides an electric rotary machine equipped with a stator coil including sequentially connected conductor segments, including a rotor having P pairs of magnetic poles, a stator core with a plurality of slots each having a plurality of conductor accommodation positions sequentially aligned in a radial direction, and M-phase windings, where M is an odd number not less than 3, each phase winding being constituted by sequentially connecting a plurality of U-shaped conductor segments. The conductor segment includes a pair of in-slot conductor portions separately accommodated into two different slots mutually spaced by a predetermined slot pitch, a U-shaped head portion continuously extending from the in-slot conductor portions and protruding from one end of the stator core so as to constitute a head side coil end, and a pair of tail conductor portions continuously extending from the in-slot conductor portions and protruding from the other end of the stator so as to constitute a tail side coil end. The paired tail conductor portions have distal ends being bonded to distal ends of tail conductor portions of other conductor segment. According to the electric rotary machine of the present invention, K inphase slots arranged successively in a circumferential direction cooperatively constitute an inphase slot group, each inphase slot accommodating the in-slot conductor portions constituting the same phase winding, where K is a natural number not smaller than 2. The slot includes S conductor accommodation position sets, each conductor accommodation position set including 1st-layer to 4th-layer conductor accommodation positions being numbered from a radially inner side and sequentially aligned in a radial direction. The phase winding includes C (=S/T) parallel coils connected in parallel to each other, each parallel coil including T (T is a natural number including 1) layer coils connected in series and selected from S layer coils accommodated in respective conductor accommodation position sets. The S layer coils are accommodated in respective conductor accommodation position sets and constituted by serially connecting K partial coils accommodated in the inphase slots arrange successively in the circumferential direction and accommodated in the same conductor accommodation position set.
According to the electric rotary machine of the present invention, K partial coils are serially connected to constitute each layer coil. The K partial coils are accommodated in the same conductor accommodation position set and accommodated in a plurality of inphase slots arranged successively in the circumferential direction. Thus, the layer coils are provided separately for respective conductor accommodation position sets. Furthermore, a total of S layer coils being thus formed is divided into C(=S/T) layer coil groups. T layer coils included in each layer coil group are connected in series, thereby letting this layer coil group serve as a parallel coil. Furthermore, C parallel coils are connected in parallel to each other to constitute a phase winding.
According to this arrangement, respective layer coil groups (i.e., parallel coils) are subjected to the same magnetic flux. Accordingly, it becomes possible to suppress variation in the electromotive force occurring between parallel circuits.
Serial connection or parallel connection of a plurality of layer coils constituting the same layer coil group (i.e., parallel coil) as well as parallel connection of the parallel coils can be easily accomplished by connecting leader lines of the layer coils. The connection between the layer coils can be easily done by using a radial joint conductor segment having a pair of in-slot conductor portions accommodated separately in a conductor accommodation position of two conductor accommodation position sets disposed adjacently in the radial direction. When the radial joint conductor segment serves as a leader line of a parallel coil, it is preferable that an insulating film covering the head portion of the radial joint conductor segment is partly removed for terminal connection.
Furthermore, the layer coil is constituted by serially connecting all of the partial coils separately accommodated in K inphase slots arranged successively in the circumferential direction. The serial connection between the partial coils can be easily accomplished by connecting leader lines of the partial coils. Furthermore, the connection of the partial coils can be easily done by using a circumferential joint conductor segment having a pair of in-slot conductor portions accommodated separately in a conductor accommodation position of two inphase slots disposed adjacently in the radial direction.
Furthermore, according to this invention, the maximum electric potential difference between respective in-slot conductor portions in the same slot becomes small. This improves the reliability in the insulation between the in-slot conductor portions.
As a result, the present invention provides an electric rotary machine with a serial-joint segmental stator coil which is preferably employable in large current and/or voltage devices or facilities. Using the circumferential joint conductor segment and the radial joint conductor segment makes it possible to simplify the connection between the partial coils and the connection between the layer coils. The entire wiring distance becomes short. The resistance loss and heat generation can be suppressed. The axial length of the coil end can be shortened. The electric rotary machine can be downsized.
In short, the serial-joint segmental stator coil of the present invention has a simple structure with a plurality of partial coils arranged regularly when seen in a cross section taken along the radial direction of the stator core. These partial coils are successively connected in the circumferential direction and in the radial direction to constitute a phase winding with partial coils being formed by serial/parallel connection circuits. Thus, it becomes possible to employ the serial-joint segmental stator coil for the large current and/or voltage devices or facilities. The layout of connection wires between the partial coils is simple. Mutual interference between the connection wires can be easily suppressed. As a result, the space for the connection wires can be reduced. Size and weight of the electric rotary machine can be reduced. Furthermore, the resistance loss and heat generation of the connection wires can be suppressed.
Accordingly, the serial-joint segmental stator coil type electric rotary machine in accordance with the present invention is preferably employed in a vehicle installing a high-voltage battery which is, for example, a 42 V-type battery having a higher output voltage level compared with that (e.g., 14 V) of a conventional battery. Furthermore, the serial-joint segmental stator coil of the present invention can be easily modified for the use in the conventional 14 V-type automotive electric rotary machine by changing the three partial coils constituting the parallel coil (i.e., layer coil) of the phase winding from serial connection to parallel connection.
According to a preferred embodiment of the present invention, the partial coil includes first and second circulation coils and a modified wave winding conductor segment. The first and second circulation coils are constituted by alternately connecting a wave winding conductor segment inserted into 1st-layer and 4th-layer conductor accommodation positions and a lap winding conductor segment inserted into 2nd-layer and 3rd-layer conductor accommodation positions. The modified wave winding conductor segment connects the first and second circulation coils and constitutes a trailing in-slot conductor portion of the first circulation coil and a leading in-slot conductor portion of the second circulation coil. The layer coil is constituted by K partial coils accommodated respectively in K inphase slots arranged consecutively in the circumferential direction and serially connected by circumferential joint conductor segments. And, the circumferential joint conductor segment constitutes a leading in-slot conductor portion of one of serially connected partial coils and a trailing in-slot conductor portion of the other of serially connected partial coils.
With this arrangement, it becomes possible to simply connect four in-slot conductor portions successively disposed in the radial direction in the same slot. It becomes possible to easily dispose numerous inphase slots which are a predetermined number of slots sequentially disposed in the circumferential direction for accommodating the same phase winding. The coil end structure can be simplified while the turn number of the partial coils can be increased.
According to the preferred embodiment of the present invention, S is equal to C. This is advantageous in that the parallel coils can be formed by the same number as that of the layer coils aligned in the radial direction.
According to the preferred embodiment of the present invention, the stator coil further includes a radial joint conductor segment having a pair of in-slot conductor portions separately accommodated in two adjacent sets of the conductor accommodation position sets and accommodated in the inphase slot having the same order in the circumferential direction. The radial joint conductor segment is connected to a leader line of the parallel coil. The pair of in-slot conductor portions of the radial joint conductor segment constitutes a leading or trailing in-slot conductor portion of two layer coils disposed adjacently in the radial direction.
With this arrangement, the parallel connection of respective parallel coils can be accomplished by using the short leader lines. In this case, the leader line is a wiring connected to an external or neutral point according to the star-connected wiring or a wiring for interphase connection according to the xcex94 connection.